Interchangeable container

ABSTRACT

The invention relates to an interchangeable container ( 1 ) for a device used to construct models. Said container forms a substantially delimiting frame, into which a workpiece platform ( 2 ) that acts as a base can be inserted. The interchangeable container ( 1 ) contains a support ( 3 ) onto which the workpiece platform ( 2 ) is introduced.

[0001] This invention relates to a job box for a pattern buildingdevice, which forms primarily a bounded frame and whose base can be aworkpiece platform mounted within the job box.

[0002] Devices for building patterns have been known in the prior artfor a long time, including laser sintering machines that have a housingarranged with a sintering or processing chamber therein. The upperworkspace of this processing chamber includes the optics of a sinteringlaser in the form of a scanner. The scanner makes up the optical systemfor directing the laser beam, which delivers the energy required tosinter the sintering material. Below this optical system is a verticallymovable workpiece platform with a material feeder and spreader situatedabove the platform, whereby the spreader serves to feed a powderedsintering material from a storage bin situated in the workspace abovethe workpiece platform.

[0003] Such a laser sintering machine is used to build the part inlayers in the central area of the vertically movable workpiece platform.Up to now, to prevent the powdered sintering material that has not beenexposed and thus not sintered from falling off of the workpieceplatform, the outer zones of the platform have usually been sinteredsimultaneously with the actual building of the part, so as to form anedge serving as a boundary for the workpiece platform.

[0004] This type of approach had many disadvantages, among them the factthat the making of a boundary for the workpiece platform requiresadditional exposure and also extra thermoplastic powder that cannot bereused.

[0005] A particular disadvantage is that any error in making theboundary will lead to an inadequately stable box type boundingstructure, which could result in deformation and consequent loss of thepart either prior to or after its removal from the vertically movableworkpiece platform.

[0006] Additionally, damage or breaks in the boundary during removal ofthe workpiece platform from the laser sintering machine result in powderfilling the lower workspace of the sintering machine, soiling it andthereby causing extra breakdowns, delays, and servicing requirements forthe laser sintering machine.

[0007] In order to overcome these known disadvantages for lasers of thestate of the art, it known from the German patent DE 198 46 478 to mounta bounded frame job box in the sintering chamber, in which the workpieceplatform is integrated as a base. Furthermore, the sintering chamber hasa carrier arrangement on which the workpiece platform is supportedduring operation of the laser sintering machine. This type of job boxhas not only a shaft-like exterior that forms the bounding frame, butalso a typical workpiece platform integrated into the shaft-likeexterior such that it is vertically movable.

[0008] The building of a part in layers means that the box base islowered successively, i.e. layer-by-layer, within the bounding frame,and the workspace above the workpiece platform is repeatedly coveredwith new powdered sintering material by a spreader in a conventionalmanner.

[0009] With such a job box, it is no longer necessary to form a boundarywhile building the part. It is fully adequate to sinter just the actualworkpiece, which is protected against deformation by being held withinthe stable job box and its unsintered sintering material therein.

[0010] Besides, this job box can be removed in one piece and replaced bya new one, making it unnecessary to wait until the respective part isstable enough to be removed without problems.

[0011] However, this type of job box has been found to have thedisadvantage that handling the workpiece platform for building partsstill calls for a significant amount of effort. For instance, if oncompletion of a pattern the workpiece platform is to be removed from thejob box and replaced by another empty platform, the task must beaccomplished in a very precise manner to ensure that the platform isagain placed and mounted precisely in the job box.

[0012] It has been found to be especially difficult when a sealing meansis present between the workpiece platform and the job box. Seals arevery important when using powdered materials for the building process,since they can affect the vertical positioning of the workpiece platformwithin the job box.

[0013] It is thus known that when the job box has engagement recessesfor vertical positioning situated above the workpiece platform, theymust covered so as to be impervious to powder. However, such types ofseals must be taken out of the job box when dismounting the workpieceplatform and replaced when mounting a new workpiece platform.

[0014] Hence, it is the object of this invention to develop a job boxthat can make it easier to mount and dismount workpiece platforms.

[0015] According to the invention, this requirement is fulfilled througha job box of the aforementioned type that includes a carrier on whichthe workpiece platform is mounted.

[0016] This means, for example, that according to the invention theworkpiece platform that can be dismounted from the job box needs to beinstalled only on the carrier, which is appropriately attached to thejob box and just carries the platform. After each replacement, theworkpiece platform thus does not need to be positioned precisely in thejob box or to be mounted or attached.

[0017] It should be emphasized that the job box according to theinvention can be mounted in all devices for pattern building known topersons skilled in the art. Hence, it is not restricted for mounting inany particular pattern building process. It can be utilized just as wellfor selective laser sintering as in a device for pattern building frommoulding sand, casting resins, and curing agents.

[0018] The statement that the workpiece platform should be mounted as abase of the job box, is not to imply that the workpiece platform shallbe arranged at the base of the job box or that it forms its lowestextremity. The term base is to be understood more as a shelf. This doesnot exclude the possibility that the job box has other bases or aspecially designed base area.

[0019] However, for the greatest ease in building a job box, it has beenshown to be advantageous to make the carrier as a frame. In such a case,the frame could encircle the inner wall of the job box, or just as wellbe a part thereof. Nevertheless, it should be built wide enough suchthat the workpiece platform can be mounted on it without possibly beingtwisted.

[0020] If the job box has braces in its lower section, they help achievemuch greater stiffness of the job box's frame design, wherebycross-braces have been shown to be especially advantageous. All othertypes of braces are conceivable, including diagonal braces.

[0021] The terms “up” and “down” used in these embodiments always implya proper operating position of the job box. Such a position is one inwhich the pattern building takes place in an appropriate device, wherebythe side of the workpiece platform mounted in the job box on which thepattern is built, faces up.

[0022] It is preferred that the lower extremity of the job box accordingto the invention has appropriate cutouts for easy access with aforklift, for enabling transport in a simple manner.

[0023] If the job box sides additionally have transport eyelets, the jobbox could be transported easily with a crane as well.

[0024] In order to enhance the stiffness of the job box even further, itis preferred to use a double-wall construction for the job box.

[0025] Although the job box and the workpiece platform couldfundamentally have any imaginable shape in a plan view, practicalconsiderations and ease of manufacturing have nevertheless found asquare or rectangular shape to be advantageous.

[0026] Basically it is feasible to have a vertical positioningarrangement that engages either under the job box or one that isintegrated as a permanent component of the job box.

[0027] However, to achieve stable conditions by utilizing a verticalpositioning means installed in an appropriate device, it is advantageousto have such means arranged mainly laterally on the sides of the jobbox, i.e. as recesses on two opposing sides running from the top down,for adjusting the vertical position.

[0028] Accordingly, the job box encompasses four sidewalls arrangedessentially at right angles to each other. The workpiece platform can bedisplaced vertically within these sidewalls.

[0029] Herein it is preferred to have a means for making the recessesabove the workpiece platform impervious to powder. This could beachieved, at least where the recesses are situated above the workpieceplatform, with a sealing means between the inside wall of the job boxand the carrier.

[0030] This occurs preferably with a type of blind, for example one madeof sheet metal, fixed to the upper edge of the job box, which restsagainst the inner box wall as the workpiece platform sinks, therebycovering the recesses.

[0031] To avoid the sheet metal from possibly becoming entangled betweenengagement catches and the workpiece platform, it is preferred to haveappropriate sliding bearings in the workpiece platform's carrier tochannel the metal sheets along the insides of the job box.

[0032] Additionally, holding magnets that function with the blind couldbe arranged in the job box. Due to the holding magnets, the blind clingsvery closely to the inner side of the rear box wall, such that eithernone or very little powder can fall into the lower area of the machine.

[0033] A holding magnet arrangement limits the choice of materials thatcan be used for job box components. Instead of a seal utilizing aholding magnet, an alternative is a felt seal between the carrier andthe inside wall of the job box, which can be loaded through springs toachieve the desired application force.

[0034] The job box according to the invention has demonstrated itsadvantage when applied in a device for pattern building from mouldingsand, casting resins, and appropriate curing agents.

[0035] Similarly, an application is also conceivable in a selectivelaser sintering device.

[0036] The preferred embodiment of the invention will now be explainedin more detail with reference to the accompanying drawings, in which:

[0037]FIG. 1 is a three-dimensional view of a job box with a mountedworkpiece platform in a cross-sectional representation of a preferredembodiment of the invention;

[0038]FIG. 2 is a front view of an enlarged section of the section shownin FIG. 1, and

[0039]FIG. 3 is a further enlargement of the section illustrated in FIG.2.

[0040]FIG. 1 depicts a three-dimensional cross-section of job box 1.This means that job box 1 is shown cut out in a three-dimensional view.Job box 1 has a total of four sidewalls arranged such as to form arectangular cross-section in plan view.

[0041] The base of this job box 1 is formed with a workpiece platform 2,mounted like the base of a cupboard or a shelf. This workpiece platform2 is in turn mounted on a carrier 3 not distinguishable in FIG. 1.

[0042] In FIGS. 2 and 3 that show front views of the schematic sectionsmore precisely, it is clear that carrier 3 is a type of frame runningmainly along the inside walls of job box 1.

[0043] Additionally, FIG. 1 shows cross-braces 4 at the base of job box1, each of which connect the opposing sidewall of job box 1. It can alsobe seen in FIG. 1 that two cross-braces each run between the sidewalls.Additionally, these cross-braces have a relatively large cross-section,which increases the stiffness of job box 1 significantly.

[0044] In order to enhance the stiffness of job box 1 even further, jobbox 1 of the preferred second embodiment of the invention has adouble-wall construction.

[0045] Additionally, at least one side of job box 1 is fitted withtransport eyelets 5, which enable transport for example with a crane,such that job box 1 could be installed with a crane in a patternbuilding device or simply transported over long distances.

[0046] As shown particularly in FIG. 2, in contrast to the solutionsknown from the state of the art workpiece platform 2 mountable in jobbox 1 is constructed in such a way that it is arranged on carrier 3shown as a frame here.

[0047] The vertical position of workpiece platform 2 is set bypositioning frame 3 on which workpiece platform 2 is mounted, such thatappropriate sealing between the inside wall of job box 1 and frame 3must occur to prevent powdered material from entering the verticalpositioning means during pattern building with such materials.

[0048] As shown especially in FIG. 1, job box 1 has recesses that runprimarily from top down and serve to vertically position frame 3. Theapplication of job box 1 for pattern building, in particular castings,enables the use of job box 1 in such a manner that catches run in thedevice's recesses 6A, 6B, 6C, and 6D and engage underneath workpieceplatform 2. These catches in turn could be attached to a lifting plate,which could be fastened through linear guides and a feed rod on to therelevant frame or the housing of the device. At the start of thebuilding process, workpiece platform 2 is raised to its highest positionand thus readied for commencement.

[0049] Recesses 6A, 6B, 6C, and 6D provided for lateral engagement ofthe catches into job box 1, for example, preferably run across the boxwall. However, as far as possible these recesses 6A, 6B, 6C, and 6Dshould not become soiled by sand or similar materials falling off ofworkpiece platform 2. Accordingly, a sealing means is preferablyincluded such that thin metal sheets 7 attached to job box 1,particularly on its top edge, press against the inside of job box 1during pattern building, for instance due to the force exerted by themoulding sand, and thereby cover up the slot. In order that these metalsheets 7, when applied in the above-described device, do not becomeentangled between a catch and the carrier or frame 3, it is preferred tohave appropriate sliding bearings in carrier 3 to channel the metalsheets along the insides of job box 1.

[0050] These sliding bearings could, for example, be the deflectionchannels 8A and 8B shown in FIGS. 2 and 3.

[0051] The sheet metal 7 now functions like a blind, by resting againstthe inner wall of job box 1 as workpiece platform 2 or frame 3 sinks andthereby covering engagement recesses 6A, 6B, 6C, and 6D.

[0052] In order to improve the sealing between frame 3 and job box 1even further, or especially against its inside wall, it is preferred tointegrate a supplementary sealing means in the lateral channel of frame3, depicted herein according to the preferred embodiment as felt seal 9.This felt seal 9 is loaded with springs 10 to achieve the necessaryapplication force.

[0053] Due to the force applied by spring 10, such a sealing means 9 canessentially balance out any unevenness in job box 1. Such a springloading means also allows avoidance of highly flexible and sensitivematerials that tend to shrink.

[0054] The advantage of such a design for job box 1, is that it becomespossible to dismount workpiece platform 2 from job box 1, for instanceby pulling it out and replacing it with another empty workpiece platform2, without the need to dismantle any of the relevant sealing meanspresent in job box 1.

[0055] Summary

[0056] Described herein is a job box (1) for a pattern building device,which forms primarily a bounded frame and whose base can be a workpieceplatform (2). The job box (1) is provided with a carrier (3) on whichthe workpiece platform (2) is mounted.

[0057] List of Referenced Numbers

[0058]1 Job Box

[0059]2 Workpiece Platform

[0060]3 Carrier

[0061]4 Cross-Braces

[0062]5 Transport Eyelets

[0063]6A, 6B, 6C, 6D Recesses

[0064]7 Seal

[0065]8A, 8B Sliding Bearings

[0066]9 Felt Seal

[0067]10 Spring

1. A job box in a pattern building device, which forms primarily abounded frame and whose base can be a workpiece platform mounted withinthe job box, characterised in that the job box (1) is provided with acarrier (3) on which the workpiece platform (2) is mounted.
 2. The jobbox according to claim 1, characterised in that the carrier (3) isconstructed as a frame.
 3. The job box according to claims 1 or 2,characterised in that braces (4) are arranged underneath the workpieceplatform (2) of the job box (1).
 4. A job box according to one of theforegoing claims, characterised in that the job box (1) is provided withan appropriate access for a forklift.
 5. A job box according to one ofthe foregoing claims, characterised in that at least one transporteyelet (5) is provided in one of the upper areas of the job box (1). 6.A job box according to one of the foregoing claims, characterised inthat the job box (1) is arranged with a double-wall construction.
 7. Ajob box according to one of the foregoing claims, characterised in thatthe carrier (3) can be positioned vertically.
 8. A job box according toclaim 7, characterised in that the recesses (6A, 6B, 6C, and 6D) runningessentially top down are provided in the sidewalls for positioning thecarrier (3) vertically.
 9. A job box according to claim 8, characterisedin that a sealing means (7) is provided at least in the area of therecesses (6A, 6B, 6C, and 6D).
 10. A job box according to claim 9,characterised in that the sealing means (7) is formed with metal sheetsfastened to an upper edge of the job box (1).
 11. A job box according toclaim 10, characterised in that the metal sheets are channelled into thejob box (1) by sliding bearings (8A & 8B) provided in the carrier (3).12. A job box according to one of the foregoing claims, characterised inthat an additional sealing means (9), particularly a felt seal, isprovided between the carrier (3) and the inner wall of the job box (1).13. A job box according to claim 12, characterised in that theadditional sealing means (9) is loaded through at least one spring means(10).
 14. Application of the job box according to one of the foregoingclaims in a device for pattern building from moulding sand, castingresins, and curing agents.
 15. Application of the job box according toclaims 1 to 13 in a device for pattern with a laser sintering method.16. Generis Generative Systeme GmbH